Aircraft electronics have become steadily more complex and advanced. This has created increasing demands for and reliance on power availability and reliability for aircraft systems such as flight control systems, electro-hydraulic actuators, navigation systems, communication systems, and entertainment systems. Recently advancements have been made in the area of circuit protection. Traditional overload protecting circuit breakers have been augmented with arc fault protection. Such augmented circuit breakers are referred to as “smart circuit breakers” (SCBs), In addition, aircraft power systems features are being developed, such as system wellness and fault location determination, which will be integrated with the augmented circuit breakers. These capabilities are utilized to further augment the real safety and availability benefits of an advanced electrical power system.
Traditional circuit protection devices focus on protecting wiring insulation from damage caused by overheating. Bimetallic analog elements in the circuit breakers respond to resistance heating of the wiring to cause the circuit breaker to trip. However, most existing commercial airplane circuit breakers do not detect and respond to arc faults. Arc faults may be caused by the chaffing and subsequent intermittent arcing that result from wires contacting the metal structure of the airplane, when the wire insulation has been worn away to expose the bare wire core.
These intermittent faults may fall outside the defined region of most circuit breakers time-current overload response curves. SCBs provide arc fault identification and circuit interruption to isolate a fault on an affected circuit. This supplemental protection is integrated into the existing power protection framework via the traditional electromechanical circuit breaker. The diagnostic information from the measured current and voltage can provide valuable electrical fault diagnostics and location information. Utilizing these same electrical measurements, many additional types of diagnostics can be provided. Some examples of the additional diagnostic capabilities that are currently in development are more precise identification and quantification of series and parallel electrical faults, identification of fault characteristics, arc fault location information and effective use of ancillary fault location equipment to minimize the time to repair affected electrical equipment. This enhanced diagnostic capability is expected to increase aircraft operating availability.
It may also be advantageous to log in-flight operating parameters for a given circuit breaker circuit. For example, a monitoring system may be possible whereby a motor load may be tracked. This may include monitoring and recording the inrush and operating current and this information may be reported to the maintenance crew during scheduled maintenance. If the current is rising over time, it could indicate bearing wear or some other type of abnormality. For example, an electronic motor that may control the control surfaces of an aircraft could be monitored. This would allow the maintenance crew to perform preventative maintenance before a failure occurs, which could result in the loss of the aircraft.
A Built-In-Test (BIT) circuit can be incorporated into the circuit breaker to detect and communicate passive failures during maintenance cycles.
Most aircraft panels contain placards that instruct the technician to remove power before opening the panel. Currently, Federal Aviation Administration regulations require that, if a circuit breaker is to be tested or diagnosed while still mounted inside of the panel, the circuit breaker remain powered. One method of detecting passive failures and interrogating the circuit breaker for trip type and other advanced trouble shooting information is disclosed in U.S. patent application Ser. No. 10/973,760 entitled “Device and System for Wireless Communications with a Circuit Breaker”, assigned to The Boeing Company of Chicago, Ill. The method provides an optical link for interrogating a circuit breaker while the circuit breaker is installed and operating in a powered panel. However, when the circuit breaker panel is not powered, the above-described features of the SCBs are unable to communicate data.
Thus, there is a need for a device that can provide power to just the electronic portion of the SCB in order to download information from the SCB when the panel is not powered.